In some semiconductor devices such as LSIs, a barrier insulating film is formed on an upper surface of an interlayer insulating film, in order to protect a circuit formed on a semiconductor substrate from the outer atmosphere. A material of the barrier insulating film is selected in accordance with the responsible atmosphere from which the circuit is to be protected.
For example, to protect a circuit from moisture, a silicon nitride film with excellent moisture resistance is formed as the barrier insulating film.
In a ferroelectric device such as an FeRAM, a ferroelectric film is deteriorated due to reduction by a reductant, such as hydrogen. Accordingly, an insulating metal oxide film, such as an alumina film, is formed as the barrier insulating film in order to protect the ferroelectric film from the reductant in the FeRAM.
However, since an insulating metal oxide film, such as an alumina film, is less chemically reactive, there are disadvantages that it is difficult to form a hole in the film by etching, and to form a hole having a stable cross-sectional shape.
Furthermore, a contact defect may possibly occur in a tungsten plug because it is difficult to form the tungsten plug in the hole due to a reaction product generated at the time of etching the alumina film.
The difficulties in forming the hole and the contact defect described above become a factor of deteriorating the yield of the semiconductor device.
In addition, when a metal wiring is directly formed on an alumina film, the alumina film is etched by over-etching at the time when a metal film is etched to form the metal wiring. As a result, barrier performance of the alumina film against the reductants is deteriorated. In view of this fact, it is also possible that a cover insulating film is formed on the alumina film for absorbing the etching, and thereafter, a metal wiring is formed on this cover insulating film.
However, this increases the number of manufacturing processes because a process of forming a cover insulating film and a process of annealing for dehydrating the cover insulating film need to be added.
To overcome such difficulties in forming the hole and the increase in the number of manufacturing processes, it is preferable that a silicon nitride film be formed as a barrier insulating film for preventing hydrogen and moisture penetration even in ferroelectric devices.
In addition, the silicon nitride film can be used as an etching stopper film in addition to being used as the above-mentioned barrier insulating film.
For example, in a damascene process useful for forming a copper wiring, a silicon nitride film and a silicon oxide film are formed in this order. Then, the silicon oxide film is etched while the silicon nitride film is used as an etching stopper film, so that a wiring groove is formed in the silicon oxide film.
However, when the silicon nitride film is formed by a chemical vapor deposition (CVD) method in the ferroelectric device to which the damascene process is applied, capacitor dielectric film is reduced and deteriorated due to hydrogen contained in film-forming atmosphere, so that the yield of the semiconductor device decreases. Accordingly, a film which rarely generates hydrogen at the time of film-forming is required as an etching stopper film used in the damascene process.
Note that techniques relating to the present application are disclosed in the specification of Japanese Patent No. 3019816, and Japanese Patent Application Laid-open Publication Nos. 2000-323572 and 2004-56099.
Among these documents, in Japanese Patent No. 3019816, nitrogen is introduced to a silicon nitride film on a gate electrode of a MOS transistor by ion implantation, and thereafter thermal processing is carried out to thermally diffuse nitrogen into an interface between an insulating sidewall and a silicon substrate.
In Japanese Patent Application Laid-open Publication No. 2000-323572, boron is ion-implanted into an organic spin-on-glass (SOG) film to reduce moisture and hydroxyl groups contained in the organic SOG film.
In Japanese Patent Application Laid-open Publication No. 2004-56099, a silicon nitride film is formed on an interlayer insulating film and a metal wiring.
In addition, patent literature 4 also discloses a technique relating to the present application.